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OBJECTIVE To determine the role of the positron emission tomography (PET) with 18F-labelled deoxyglucose in the identification of prostatic cancer in the iliac and obturator lymphatic nodes before radical prostatectomy, and in the localization of relapse in patients in biochemical progression.

PATIENTS AND METHODS Twenty-one patients were divided into two groups. Group A consisted of 11 men diagnosed with organ-confined prostate cancer, where attention was focused on the iliac and obturator lymphatic nodes, the results being compared with the pathological anatomy obtained from surgical procedures. Group B included 10 patients treated by radical prostatectomy, radiotherapy or orchidectomy and who were in biochemical progression, in whom the aim was to identify recurrence of the disease.

RESULTS In none of the 11 patients of group A who had undergone radical prostatectomy were deposits of radiotracer identified in the area of the iliac and obturator nodes which would indicate node metastases. However, the histopathological analysis of these nodes showed tumour in three patients. In group B the PET scans showed recurrence of prostate cancer (by deposits of radiotracer) more clearly than did computed tomography (CT) in two patients (both with recurrence in soft tissue). In one patient bone scintigraphy identified a lesion compatible with prostatic disease in the bone; this was clinically confirmed but was not identified by PET.

CONCLUSION PET, using deoxyglucose labelled with 18F, cannot reliably identify prostatic adenocarcinoma in the iliac and obturator lymph nodes before surgery; other tracers may give better results. To locate relapses in patients with biochemical progression, PET seems to have better sensitivity than CT when identifying diseases in soft tissues and is possibly inferior to bone scintigraphy in detecting bony metastases.